Electrodeposition as a coating application method involves the deposition onto a conductive substrate of a film-forming composition under the influence of an applied electrical potential. Electrodeposition has gained popularity in the coatings industry because it provides higher paint utilization, outstanding corrosion resistance, and low environmental contamination as compared with non-electrophoretic coating methods. Both cationic and anionic electrodeposition are used commercially, with cationic being more prevalent in applications desiring a high level of corrosion protection.
There are a number of decorative applications in which it is desired to control the gloss of a coating layer applied by cationic electrodeposition. Electrodeposited coatings having high gloss levels are readily achievable, but acceptable cationically electrodeposited coatings with a low gloss level have been more difficult to prepare. Addition of traditional flatting agents, such as silicas and alumina silicates, to electrodepositable coating compositions will produce the desired gloss levels, but these flatting agents are often much more dense than other bath components and will settle in the electrocoat baths. Continuous recirculation must therefore be employed to maintain paint homogeneity, even when the bath is not in use. The need for continuous recirculation leads to higher capital equipment costs, higher maintenance costs, and higher energy costs. In addition, the density of these flatting agents often results in coatings with an uneven appearance that lacks smoothness, especially when coating complex parts and areas in which mixing is not consistent.
As a result, it would be desirable to provide cationic electrodepositable compositions with good anti-settling properties that provide smooth, low gloss coatings.